We plan to investigate myelinated and genetically amyelinated nerves during development, degeneration, and regeneration, to determine the mechanisms underlying the dynamic cellular transactions between myelinating cells and axons. We shall concentrate on those morphological specializations relating to the nodes of Ranvier and the paranodal regions of elaborate, intimate contact between glia and neuron. We shall employ freeze-fracture, thin section and thick section (using high voltage) electron microscopy, using active and inert tracers to disclose compartments and channels, and inserting molecular-specific labels to localize and characterize membrane proteins in these functionally specialized regions. We aim to determine the cellular mechanisms involved in the creation, maintenance and control of supramolecular organization existing through, within and surrounding glial and axonal membranes in myelinated nerves.